PhD Scientific Days 2022

Clinical Medicine V. (Poster discussion will take place in the Aula during the Coffee Break)

Analysis of circular RNA expression in adrenocortical tumors

Text of the abstract

Introduction. Incidental adrenal tumors (5-7% prevalence) are predominantly represented by benign adrenocortical adenomas (ACA) with excellent prognosis, however, rarely (incidence: 0.7-2/million/year), adrenocortical carcinoma (ACC) occurs with a five-year survival of less than 30%. Differentiation of ACA and ACC could be rather challenging. Circular RNAs (circRNAs) have been implicated as relevant factors in tumorigenesis but has not been studied in adrenocortical tumors, yet. CircRNAs are thought to be involved in the epigenetic regulation along with the microRNAs.
Aim: To explore the circRNA expression profiles in benign and malignant adrenocortical tumors by next-generation sequencing followed by RT-qPCR validation.
Materials and methods. Formalin-fixed, paraffin-embedded (FFPE) samples including 8 ACC, 8 ACA and 8 normal adrenal cortex (NAC) were used. To maximize purification process for low abundance circRNAs, we applied RNase R digestion, polyadenylation and depletion method. For expression profiling of known and novel circRNAs, MiSeq (Illumina) next-generation sequencing (NGS) platform was used. RNA-seq reads were mapped to GRCh38 reference genome. Data matrix was generated with circRNAprofiler (Bioconductor) and limma-trend algorithm was used to evaluate the differentially expressed circRNAs. Three different circRNA detection tools (CIRI2, CircExplorer2, AutoCirc) were used for the discovery of de novo circRNAs. The top 5 most differentially expressed circRNAs were measured by RT-qPCR in an independent ACC (11), ACA (7), NAC (8) cohort. In silico predicted microRNA sponging of differentially expressed circRNAs is currently studied by TaqMan RT-qPCR assays on the same former samples.
Results. Significantly differentially expressed circRNAs have been revealed between ACC versus ACA and ACC versus NAC cohorts by NGS. Out of the top 5 significantly different circRNAs (PHC3, FCGBP, TIMMDC1, KDM4C, MAN1A2) PHC3 could be confirmed to be significantly overexpressed in ACC and ACA vs. NAC samples by RT-qPCR.
Conclusion. We were able to find novel and differentially expressed circRNAs in adrenocortical tumors. There is significant difference in expression of PHC3 in ACC and ACA versus NAC cohorts validated by RT-qPCR. In silico predicted miRNA interactions is currently studied by RT-qPCR.

ÚNKP-21-3; (NKFIH) K134215